Interior and exterior construction boards with cores of plaster, cement, or hybrid materials, such as cement boards or gypsum boards, are used in a wide variety of indoor and outdoor structural applications. For example, fairly recent gypsum/cement boards are used as a support surface for overlying materials such as wood siding, stucco, aluminum, brick, tile, stone aggregate, and marble. Also, gypsum/cement boards are used in exterior insulating systems, commercial roof deck systems, masonry applications and exterior curtain walls.
Generally, gypsum boards contain a core formed of a gypsum material and low-density fillers that are interposed between two facing layers. Known methods for making gypsum boards consists of providing a continuous feed of facing material and depositing a gypsum slurry onto the bottom surface of the facing material. A second continuous feed of facing material is then applied to the top surface of the slurry. The slurry is dried to harden the gypsum composition and to integrate the facing material into the cement board. The gypsum board is subsequently cut to a predetermined length for shipping and eventual use.
Facing materials advantageously contribute flexural, nail pull resistance, and impact strength to the high compressive strength but elongationally brittle material forming the cementitious core. In addition, the facing material can provide a durable surface and/or other desirable properties to the gypsum board.
Although paper sheets have long been used as the facing material for gypsum boards, facing materials formed of a fibrous mat have enjoyed a substantial increase in popularity. Glass fiber facings provide increased dimensional stability in the presence of moisture, biological resistance, and greater physical and mechanical properties than normal gypsum boards. These facing sheets are formed as randomly oriented, fibrous glass mats.
Fibrous non-woven mats or fabrics have found particular utility where the dimensional stability, fire resistance, biological resistance, nail-pull resistance, and flexural strength inherent in such materials are combined with a continuous, soft-touch coating.
Typical coated fibrous mats, as described above, offer many advantages over non-coated mats but have disadvantages as well. For example, off-line coated formulations are not as cost effective as direct wet formed mat products.
It is therefore highly desirable to provide a universal coating for a gypsum facer that can be used in a wide variety of gypsum board applications, from decorative to purely functional gypsum boards. It is also highly desirable to provide a gypsum facer that is cost effective.